1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to multi-piece golf balls having a center, a mid layer and a cover.
2. Description of the Related Art
Flight performances are important for golf balls. The flight distance correlates with the speed of the ball immediately after the impact. This speed correlates with the resilience performance. With respect to the resilience performance, a variety of proposals have been made.
Japanese Unexamined Patent Application Publication No. 2006-223874(US 2005/176523) discloses a golf ball having a center, a first mid layer, a second mid layer and a cover. The resilience coefficient of a spherical body including the center and the first mid layer is greater than the resilience coefficient of the center. The resilience coefficient of a spherical body including the center, the first mid layer and the second mid layer is greater than the resilience coefficient of a spherical body including the center and the first mid layer. The resilience coefficient of the golf ball is greater than the resilience coefficient of a spherical body including the center, the first mid layer and the second mid layer.
Japanese Unexamined Patent Application Publication No. 2006-223875(US 2006/189413) discloses a golf ball having a center, a first mid layer, a second mid layer and a cover. The resilience coefficient of a spherical body including the center, the first mid layer and the second mid layer is greater than the resilience coefficient of the golf ball. The resilience coefficient of a spherical body including the center and the first mid layer is greater than the resilience coefficient of a spherical body including the center, the first mid layer and the second mid layer. The resilience coefficient of the center is greater than the resilience coefficient of a spherical body including the center and the first mid layer.
Japanese Unexamined Patent Application Publication No. 2006-230661 discloses a golf ball suitable for golf players who hit with a low head speed. This golf ball has a core, a mid layer and a cover. In this golf ball, a highly resilient material is used for the mid layer.
The golf players place great importance also on spin performances of the golf balls. Great back spin rate results in small run. For golf players, golf balls which are likely to be spun backwards are apt to be rendered to stop at a targeted position. Great side spin rate results in easily curved trajectory of the golf ball. For golf players, golf balls which are likely to be spun sidewise are apt to allow their trajectory to curve intentionally. The golf balls that are likely to be spun are excellent in control performances. High-level golf players particularly place great importance on control performances upon shots with a short iron.
For golf players, the stability of the spin rate is also important. To attain the trajectory intended by a golf player may be difficult with the golf balls accompanied by greatly varying spin rate. The control performance also depends on the stability of the spin rate.
The resilience coefficient correlates with the rigidity of the golf ball. Highly rigid golf balls generally have a great resilience coefficient. However, when such highly rigid golf balls are hit by golf players with less power, sufficient flight distance may not be attained because the golf ball is not appropriately deformed when the golf ball is hit by the golf players with less power, i.e., golf players who hit with a low head speed. Furthermore, inappropriate deformation behavior also inhibits the control performance. An object of the present invention is to provide a golf ball that is excellent in the flight performances and control performance.